Sensors of the general type discussed in the context of the present invention are generally known; see, e.g., EP 0 247 850. Implantable sensors for the in vivo-measurement of medically important analytes like glucose or lactate are based on electrochemical enzymatic detection of the analyte. The most common approach is the use of an oxidase to oxidize an analyte, e.g. glucose, with subsequent reduction of oxygen to hydrogen peroxide and amperometric detection of the hydrogen peroxide by a working electrode of the sensor. Another approach in the field of in-vivo sensing bypasses the use of oxygen/peroxide as a mediator couple by employing synthetic redox mediators for glucose conversion without oxygen. In that case, synthetic redox mediators are built into the sensing element. An example for this approach utilizes poly(biimidizyl)osmium complexes as redox mediators in conjunction with enzyme, as described by Feldmann et al. in Diabetes Technology and Therapeutics, 5, 769 (2003).
Despite intensive research and development efforts there are at present no implantable sensors available which measure medically important analytes like glucose reliably over extended periods of time.
It is an object of the present invention to provide a way to improve the reliability and longevity of amperometric sensors for in vivo-measurements of an analyte concentration in a body fluid.